The Argentina star, whose current deal expires in the summer of 2018, has yet to agree new terms, sparking speculation he could leave the Catalan club, with Premier League big guns Manchester City, now managed by Pep Guardiola, linked.
Bartomeu, however, is confident the 29-year-old will remain at the Nou Camp.
Speaking at the announcement of a lucrative four-year sponsorship deal with Japanese technology company Rakuten, Bartomeu said: “I believe we’ve got a team with incredible players, all of them. There is nonetheless a leader of course, Leo Messi, he is well known and popular all over the world.
“We’re all convinced, we’re all positive Leo Messi will end his sporting career in Barca.
“All the members of Barca believe this is how it has to be, because he is the player that in the last few years has brought us sporting success.”
The new sponsorship agreement will see Rakuten replace Qatar Airways on the front of Barca’s shirts from the start of next season and, according to fcbarcelona.com, will earn the club €55m a year.
Bartomeu revealed Barca defender Gerard Pique and his popstar wife Shakira helped the club negotiate the deal with Rakuten chief executive Hiroshi Mikitani.
“Gerard Pique and his wife Shakira are very close friends with Mr Mikitani,” Bartomeu said. “It was in the summer of 2015, Gerard organised a dinner in San Francisco during our summer tour. At that dinner we met Mr Mikitani, who was, for us, an incredible person. We talked about the future, about his interest in FC Barcelona and we started at that moment conversations and Gerard Pique helped us a lot to meet Mr Mikitani, so we are very grateful to him.”
Messi was on international duty this week, and his stunning free-kick helped Argentina give their World Cup qualification hopes a timely boost with a 3-0 win over Colombia.
La Albiceleste went into the game at San Juan sixth in the South American qualifying table, with the top four qualifying automatically for Russia 2018 and the fifth-placed side entering a play-off against the top Oceania side.
However, a Messi opener and goals from Lucas Pratto, and Angel di Maria - with Messi creating both goals - helped Argentina end a four-match winless run and leapfrog their opponents into fifth. Nevertheless all is not well in Argentina.
Messi led the squad in a media boycott as he announced no player would speak to the press due to perceived unjust treatment.
Captain Messi was flanked by the the entire squad as he told journalists about the boycott in the press conference room at the Estadio San Juan del Bicentenario following the World Cup qualifying win over Colombia.
They staged a protest against allegations made against Ezequiel Lavezzi and Messi, surrounded like the likes of Sergio Aguero, Pablo Zabaleta and Javier Mascherano, and revealed the squad were imposing an indefinite media boycott.
He said: “We are here to tell you we are not going to talk to the press any more - you know why. We have received a lot of accusations and disrespect, but the accusation against Pocho (Lavezzi) is very serious. We are sorry we have to do this...but we’re not going to talk. We know a lot of you (journalists) are not involved in this, but this is what we’ve decided. You can criticise us if we play well or badly, but getting into one’s private life and such serious accusations - no.”
After Messi had finished speaking the squad walked out of the press room. Lavezzi, the former Napoli and Paris St Germain forward now with Hebei China Fortune, was accused by a journalist on Twitter of smoking marijuana after a training session.
He strongly denies the allegation and announced on Twitter he is taking legal action against the journalist responsible for what he called “false statements” which have caused “serious damage” to his family and his work.